The present invention relates to an improved method of brewing coffee and a coffee brewing device therefor. More particularly, the invention is directed to a method of brewing coffee and a coffee brewing device wherein the device is hand-held by means of a self-supporting handle thereon while a porous coffee containing portion of the device is at least partially submerged in a brewing liquid and stirred to brew a single cup of coffee with an improved extraction efficiency and, hence, in a relatively short brewing time.
Heretofore, many devices and methods have been proposed for brewing ground coffee one cup at a time. For example, in U.S. Pat. No. 2,123,054, a bag-like, coffee retaining receptacle is disclosed. The brewing time required with this device is indicated as five to eight minutes. The patentees state that the device can be gently vertically agitated in the cup to produce a cup of coffee in a shorter period of time. In one embodiment, an inner circulating element in the form of a perforated conical hollow body is employed within the ball-like receptacle. This hollow body allegedly exposes the body of coffee more quickly to the water to produce a quicker action in the making of coffee. Notwithstanding, applicants have found that the time required for brewing coffee with such a device is still on the order of several minutes or more, even when the device is agitated vertically in the manner indicated by the patentees. The coffee produced after such a period with this type of device may also lack the full bodied flavor and aroma one normally expects from a good cup of brewed coffee. The temperature of the coffee may also be less than "hot" when long brewing times are required, especially where cream is added to the coffee. Other devices which have been proposed are shown in U.S. Pat. Nos. 3,154,418 and 4,215,628, and in British Patent No. 1,601,335.
It is also known to provide such devices with special arrangements for forcing water through the coffee-retaining brewing device. For example, U.S. Pat. No. 3,607,302 discloses a conically shaped flow-through type coffee bag which is repeatedly dipped in water to force water through the bag as the bag is pulled upwardly. In a similar manner, the bag in U.S. Pat. No. 4,278,691 is pulled upwardly and lifted out of the cup so that water captured in a reservoir portion of the apparatus moves downwardly through the coffee receptacle portion of the apparatus. Another apparatus is disclosed in U.S. Pat. No. 3,935,318 wherein water is circulated through the device by creating a pumping action or forced circulation with oscillatory movement of a flexible upper membrane of the device. Water flows in and out of the device through perforations in the lower surface thereof. A further example of an apparatus for making a coffee beverage using a pump-like action is disclosed in U.S. Pat. No. 4,211,156.
The pumping or other special arrangements of the aforementioned known devices are provided with a view toward enhancing the efficiency of the brewing process and therefore reducing the brewing time. However, such devices may still require a considerable period of time to brew a cup of coffee from ground coffee and the flavor of the coffee may be found lacking. These devices are also disadvantageous in that their construction is relatively complex. The necessity of having to pump or otherwise specially manipulate the devices to effect brewing is also something that the consuming public can find unacceptable or impractical in a device for conveniently producing a cup of brewed coffee.
More recently, in U.S. Pat. No. 4,410,550, an apparatus and method for making a beverage are disclosed wherein the extraction is reportedly improved by mixing coffee with water using air agitation of the coffee. The device requires the user to blow on a conduit in the form of a common drinking straw which is connected to a porous, coffee containing chamber. While relatively simple in design, one drawback with this type of device is that it requires the user to blow with his or her mouth into the air tube to agitate the coffee for brewing. This exposes the user's mouth and face to possible scalding or burning from the hot water contained in the drinking cup, and, in itself, may be an uncomfortable and unacceptable manner of producing a cup of coffee.
Thus, there continues to be a need for an improved coffee brewing device and method which can be used to quickly and inexpensively produce a cup of good, hot coffee in a manner which is comfortable, safe and readily acceptable to the consuming public.
Accordingly, an object of the present invention is to provide an improved method and device for brewing coffee, one cup at a time, which enable rapid brewing of ground coffee without necessitating the use of special pump devices or other relatively complex, possibly costly and impractical arrangements. An additional object of the invention is to provide an improved method and device for rapidly brewing ground coffee, one cup at a time, which enable the user to produce a cup of coffee in a manner which is comfortable and safe to the user.
A further object of the invention is to provide an improved method of brewing coffee and a coffee brewing device which are simple and inexpensive while, at the same time, providing a high extraction efficiency during brewing and, hence, a rapid brewing of a good, aromatic, flavorful and hot cup of coffee from ground coffee. More particularly, it is an additional object of the present invention to provide an improved coffee brewing method and coffee brewing device which are useful to produce a flavorful cup of coffee in a relatively short period of time, such as within 40-60 seconds, which method merely requires the user to stir the device in the liquid in a manner which is comfortable and safe to the user.
These and other objects of the present invention are attained by a preferred method of brewing coffee of the invention which comprises the steps of providing a coffee brewing device having a porous housing containing a supply of ground coffee with a self-supporting handle dimensioned to be hand-held attached to the housing for positioning and stirring the housing in a liquid to effect brewing of the coffee and wherein the housing further includes vent means for venting gases from an interior portion of the housing during brewing, at least partially submerging the housing in the liquid and stirring the housing in the liquid using the handle to produce a flow of the liquid within the porous housing, and controlling the flow of liquid produced within the housing to create turbulence therein to agitate the ground coffee while venting gases generated the brewing from an interior portion of the housing through the vent means for rapid brewing of the coffee. According to the several disclosed embodiments of the invention, the step of controlling the flow of liquid produced within the housing by the stirring involves interacting the flow in the housing with at least one element connected to the housing to create turbulence in the liquid flow to agitate the ground coffee for rapid brewing. Creating turbulence in the detained water volume to agitate the coffee grounds while venting the gases within the housing enhances the water contact with the coffee grounds and increases the extraction rate of the ground coffee so that a flavorful and aromatic coffee beverage can be produced in a relatively short period of time, such as 40-60 seconds.
According to one disclosed embodiment of the invention, the step of controlling the flow of liquid to create turbulence therein includes changing the direction of the liquid flow in the housing by providing at least one baffle in the flow path of the liquid. Another technique of the invention which may be used to create turbulence in the flow of liquid within the housing includes changing the direction of the liquid flow in the housing by providing the housing with at least one porous wall which can move a substantial distance inwardly and outwardly with respect to adjacent portions of the housing during the stirring. The fluttering or sudden movement of the porous wall which occurs when there is a change in the stirring direction creates a turbulence in the liquid flow within the housing for agitation of the coffee grounds. A still further manner of effecting turbulence is achieved by providing an irregular surface on the baffle and/or housing side wall to disrupt the laminar flow.
A preferred form of the improved coffee brewing device of the invention comprises a housing containing a supply of ground coffee, the housing being at least partially submersible in a liquid to effect brewing of the coffee, a self-supporting handle dimensioned to be hand-held attached to the housing for facilitating positioning and stirring of the housing in the liquid, the housing including at least one porous wall which permits the liquid to enter the housing when the housing is submerged at least partially in the liquid and vent means for venting gases from an interior portion of the housing, the gases being generated during brewing, and wherein the housing includes means for controlling a liquid flow produced in the housing during stirring to create turbulence therein to agitate the ground coffee while the gases are being vented from an interior portion of the housing by the vent means for rapid brewing of the coffee.
According to one disclosed embodiment of the device, the means for controlling the liquid flow includes at least one baffle which is connected to the housing and which extends transversely to a direction of flow induced in the housing during stirring for changing the direction of the liquid flow. More particularly, the baffle extends essentially vertically from a lower portion to an upper portion of the housing. The surfaces of the baffle are arranged at an acute angle with respect to the directions of liquid flow produced in the housing during a back and forth stirring motion of the device. These surfaces of the baffle interact with the liquid flow within the housing to change its direction and create turbulence therein to agitate the ground coffee for rapid brewing. The vertically extending baffle defines a pair of at least partially closed compartments within the housing which contain and retain coffee during brewing.
In another form of the device, the baffle is positioned on a side of the housing. More particularly, a pair of baffles are provided on opposite sides of the housing in laterally staggered relationship. Liquid flow produced within the housing during the stirring is caused to interact with these baffles to change the direction of the liquid flow and cause a turbulence therein to agitate the coffee for rapid brewing.
According to a further form of the device, the baffle is asymmetrically rotatably supported within the housing so that the stirring movement of the device causes the baffle to rotate. This creates turbulence in the detained water volume within the housing to agitate the ground coffee for rapid brewing.
The means for controlling the liquid flow to create turbulence according to another embodiment of the device of the invention includes forming the at least one porous wall of the housing of a flexible porous material which is supported on the housing so as to be movable a substantial distance inwardly and outwardly with respect to the adjacent housing during stirring to create turbulence in the liquid flow within the housing to agitate the ground coffee for rapid brewing. In a disclosed form, the porous wall is provided with at least one fold therein so that the porous wall expands a predetermined amount in response to pressure exerted thereon during brewing by generated gases, by expansion of the coffee grounds, and by water pressure from stirring. The porous wall in its expanded state is movable a substantial distance inwardly and outwardly with respect to the adjacent housing during stirring. It is this fluttering movement of the porous wall which occurs with changes in the stirring direction that creates turbulence in the detained liquid within the housing.
The extraction rate of the aromatic and flavor components of the coffee is increased by the turbulence created agitation of the ground coffee which results from these respective features of the invention. Although vent means for venting generated gases from an interior portion of the housing need not be provided in a device according to the invention, it has been found that the efficiency of the brewing process with a device of the invention can be further increased if such a vent means is provided. Water contact with the grounds is facilitated by permitting the generated gases to readily escape the portion of the housing containing the coffee grounds. In one form of the invention, a vent means is formed in the handle of the device and includes a conduit extending through an axial length of the handle. The conduit establishes fluid communication between the interior portion of the housing and the surrounding atmosphere.
The vent means according to another form of the invention includes a vent chamber provided in an upper portion of the housing from which generated gases can readily escape. A wall is provided in the housing for preventing the supply of ground coffee from moving into the vent chamber during brewing. The wall is perforated to permit the gases to flow through the wall into the vent chamber, while substantially preventing a flow of the supply of ground coffee into the vent chamber. The plane of the wall is preferably inclined at an acute angle with the longitudinal direction of the device with the wall being located at a distance from the lower end of the device such that the wall is at least partially above the water level during stirring.
In the several illustrated embodiments of the invention, the housing of the device includes opposed relatively narrow side walls with opposed relatively wide walls of the housing extending intermediate the narrow side walls. At least a substantial portion of each of the wide walls is porous to permit liquid permeation through the housing during stirring. The porous walls of the housing are constructed of porous filter paper, which allows liquid to permeate or be absorbed into the housing but which retains the particles of ground coffee in the housing. The relatively narrow side walls of the housing are formed of an impermeable, thin flexible plastic material which tends to retain its shape in the boiled water during stirring but, once the brewing device has been utilized to brew coffee, is sufficiently flexible that it can be removed from the coffee and squeezed with the fingers to drain coffee from the interior of the housing without scalding or burning the fingers.
These and other objects, features and advantages of the present invention will become more apparent from the following description when taken in connection with the accompanying drawings which show, for purposes of illustration only, several embodiments in accordance with the invention.